1. Field of the Invention
The present invention relates to physical bodies which are connected together into an assembly by a threaded fastener. More particularly, the present invention relates to assemblies provided by metallic bodies connected by headed, threaded fasteners wherein the fasteners are inserted into blind bores of one of the bodies of the assembly.
2. Discussion of Related Art
In the most recent three decades, there has been a constant quest to improve the fuel economy of automotive vehicles. This quest for fuel economy is driven by both environmental and national defense considerations. To increase fuel economy three approaches have been utilized. The first approach is to increase efficiency of the engine which powers an automotive vehicle. The second approach is to lower the aerodynamic drag of a vehicle. The third approach is to lower the weight of the vehicle.
To lower vehicle weight and aerodynamic drag often requires a reduction in vehicle the size of components. Smaller sized components often dictate the utilization of smaller fasteners.
One such smaller component is a caliper assembly for an air-actuated disc brake of a truck-like vehicle. Caliper assemblies have various parts which are connected by threaded fasteners. The fasteners must not only endure large amounts of vibration, but must also endure thermal cyclic loading, resultant of brake operation. Because the brake calipers are adjacent to a vehicle's wheels, it is preferable that threadably connected subassemblies of the caliper utilize blind bores so as to inhibit infiltration of moisture, dirt and other contaminants which can degrade the threaded connections.
To reduce component size, it is preferable that the threaded fasteners utilized be as short as possible in order to meet clearance requirements of the brake caliper with other portions of the vehicle brake and vehicle suspension systems.
Through empirical experience it has been found that in certain situations it is difficult to maintain clamping load between different components of the disc brake caliper assembly. One of the most obvious solutions to rectify or to increase clamping load is to add a nut on the opposite end of the fastener so that two connected bodies may be compressed together by torsion of a fastener, such as a bolt. However, the use of a nut with a bolt requires typically an increase in length of the bolt. Additionally, the use of a nut with a bolt prevents the utilization of a blind bore. If the clamping load by a group of fasteners which connect one component with another component is insufficient, additional fasteners may be required.
The use of additional fasteners is disadvantageous from a cost standpoint of increased fastener costs and increased machining operations to drill and tap the additional threaded bores which receive the fastener. Interference-type threads have empirically been used in an attempt to increase clamping load. However, interference-type threads typically do not significantly add to clamping load and additionally add to the disadvantage of increasing difficulty of disassembly for maintenance operations. Also, interference-type threads greatly increase the cost of initial assembly of the brake caliper.
An increase of thread quality can lead to slight increases of clamping load. However, such increases are typically not as great as desired. Increases in thread quality also lead to increased fabrication cost.
It is desirable to provide an assembly of threadably connected components wherein clamping load can be maximized while still utilizing threaded fasteners which are inserted into blind bores having lower cost precision threaded connective arrangements.